Separation of products from wood



Feb. 18, 1947. A. A. REITER ErAL 2,416,270

SEPARATION OF PRODUCTS FROM WOOD DISTILLATE BY FRCTIONAL DISTILLATION Filed Sept. 29,r 1942 2 Sheets-l-Sheet 1 fer/'al af 25 6. 4

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SEPARATION l0F PRODUCTS FROM WOOD DISTILLATE Dlla/bn d Abu/r 017 che? Lef/VX Pressure .50

Feb. 18, 1947.

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l Patented Feb. l18., 1947' `sEPARATroN oF PRODUCTS FROM woon nrs'rmLATE BY Fnac'rroNAL Drs'rnlLA- TION Alfred A. Reiter and Floyd L. Beman, Marquette,

Mich., assignors to Cliffs Dow Chemical Company, Marquette, Mich., a corporation of Michi- Application september 29,1942, sei-iai No. 460,167-

Iny

2 Claims. `(Cl. 202-40) Although the'character of the acetic oil cbtained as described above may vary somewhat, depending upon the exact manner of` carrying out the several operations of vthe process, it is usually obtained as a substantially anhydrous, non-viscous, acidic liquid which is at least partiallysoluble in water or dilute acetic acid and which is miscible with most organic solvents. The

methods also effect a partialseparation of the materials previously obtained as tars into settled tars on the one hand and dissolved portions consisting essentially of mixtures of non-terry organic compounds on the other hand, these products appearing separately as the result of4 different operations in the process..y One such dissolved portion herein designated as acetic oil to distinguish it from other portions of tars or oils appearing in the process consists of a liquid product which steam distills along with *,acetic acid from the settled and demethanolizedpyroligneous acid and which remains as a residue upon removing the water and a major portion of the low-boiling aliphatic acids; e. g., formic, acetic, and propionic acids. In one typical process the acetic oil is obtained by steam-distilling'4 the demethanolized and settled pyroiigneous acid, extracting the aqueous distillate'with an when the crude acid of United States Patent 2,197,069 is fractionally distilled under reduced4 pressure to recover therefrom a major proportionof the acetic acid. Acetic oil obtained in this manner amounts to a substantial portion of the total organic products obtained from pyroligneous acid produced in the destructive distillation of hardwoods, such as maple, beech, birch, and oak. However. little, if any, information as to the composition of this oil has heretofore been ,available other than that it contains phenolic substances and that small amounts of volatile acids, e. g., acetic and propionic acids, maybe recovered from it by steam distillation.

specific gravity ofthe acetic oil is usually greater than'1.0.

Attempts to recover valuable components from acetic oil by conventional methods involving treatment with alkalies or acids or by distillation at atmospheric pressure lead to excessive decomposition. Fractional distillation under reduced pressure by the ordinary procedure. even with a high reflux ratio, is not feasible because the gradual and substantially constant rise of the distilling temperature and the variation between succeeding lots of acetic oil mentioned above make it impossible to select accurately a fraction rich in a single component.` Consequently, acetic oil has vheretofore been used principally as fuel.

It is an object of this invention to provide a method whereby valuable compounds may be isolated readily from the acetic oil described above.

A further object isr the economical isolation of certain compounds not previously known to ex-v ist among the products obtained by the destructive distillation of wood.

As stated above; the fractional distillation under reduced pressure of the acetic oil and the selection of fractions in the usual manner does not permit the accurate'selectionv of a fraction rich in a single component due to. the gradual but substantially constant rise in the distilling temperature. This is illustrated by Figure 1 of the drawingin which the vapor temperatures of the distillingl material noted during a vacuum distillation of a representative sample of acetic oil are plotted .against the per cent by weight of material distilled. The break noted in the curve at 50 per cent distillation is due to the lowering of the pressure at this point from 50 millimeters to about 22 millimeters to avoid possible decomposition in the still.

We have found, however, that when acetic oil' is distilled with reflux, the specific gravity of the material distilling passes throughv a series of regions in which its average rate of change with respect to the amount of material distilled is alagainst the per cent byweight of material distilled. Regions in which the average rate of change of the specific gravity with respect vtothe amount of material distilled isgrelatively small are represented by portions of thel curve near maximum VAor minimum points, at. which points the rate of change of the specific gravity is actually zero, and by portions of the curve which approach parallelism with the distillate axis butv which may not actually pass through a maximum or minimum point. Regions in which the `rate of change of the specific gravity vwith respect 'to the amount of material distilled is relatively large are represented by portions of the curve which approach parallelism with the specific gravity axis. We have further found that when the specific gravity is passing through the regions of relatively small average rate of change with respect to the amount of material distilled, the material distilling is rich in a single component. It is thus possible to distill the acetic oil through an elcient fractionating vcolumn-'and to select a fraction of distillate rich in 4a single `component by beginning the collection of the' fraction when the specific gravityof the material `distilling is approaching a region wherein its avgerage rate of change withl respect to the amount fof material distilled is relatively -small, and terminating the collection of the fraction when the lspecic gravity of the material distilling' has ,passed through and is receding fromthis region. Portions of distillate from which crystals sepa- ;rate may be filtered andthe 4specific gravity of the liquid portion determined. A component `which may be 'present only in minor amounts in the mixture being distilled may, unless an excessive amount of reiuxis maintained, cause only la slight variation in the vrate of change of the `specific* gravity of the material distilling. lsuch instances it may bemore economical to c olllect' the minor. component in a fraction along `with a major component and, if desired, to subsequently effect separation of one or more com- 'Fponents from the collected fraction.

course, understood that in certain instances it lmay also be advantageous to'collect two or more iof the major components of the mixture in the same fraction, in which case the collection of the fraction may be started when the rate of change of the specific gravity of the material distilling indicates that the latter is becoming richer in the lowest boiling desired component and terminating the collection of the fraction when the rate (of change of the specific gravity of the material Idistilling indicates that the latter is becoming lless `rich `in the highest boiling desired component. Although the distillation may be carried "out at any desired pressure, it is usually carried compounds have not previously been known -to exist among4 the components of pyroligneous acid and the purication of which are described in our concurrently filed and co-pending applications Serial No. 460,168, now Patent 2,401,274,

granted Mam 28, 1946, and Serial No. 508,424.

Fractions rich in higher phenols, such as guaiacol and creosol..may alsovbe `collected kand treated to recover the higher phenol in purified form as described in our concurrently led and co-pending applications Serial No. 460,170, now Patent 2,400,- 466,` and Serial No. 460,171.

tralized and then fractionally distilled, the desire'd fractions-being collected in the manner previously described.- Fractions containing free acids, vsuch as acetic and butyric acids are, of course, not obtained by fractionally distilling the neutralizedv acetic oil and the specific gravity range over which any desired fraction is collected v may be somewhat different than when fractionally distilling the unneutralizedl oil; but otherwise the character and relative proportions' of the fractions collected are substantially the same irrespective of the order in which the neutralization and fractional distillation are carried out. In Figures 3 and 4, respectively, of the drawing the distilling temperature and the specific gravity of the material distilling observed during a distillation of a neutralized representative sample of acetic oil are shown vplotted against the per cent by volumeV of material distilled. Regions in which the average rate of change of the speindividual` fractions obtained by distilling theout under sub-atmospheric pressure and preferaf 1 bly below 400 millimeters of mercury since some 3 decomposition of the less heat-stable components may occur at; higher temperatures. x Although the collection of a fraction rich in a particular `component is controlled by means of 1 specific gravity determinations, it is advantaciflc gravity vof the material distilling with respect to the amount of material distilled are relatively small are illustrated in Figure 4 by' the maximum and minimum points of the-curve as well as 'by the region where the curve approaches parallelism with thedistillate axis, and these parts of the curve represent regions where' the material distillingl is rich in a single component of the neutralized acetic oil.

The neutralization of the acetic oil or of the acetic oil is usually accomplished by adding an amount ofl an aqueous alkali such as `sodium carbonate, potassium carbonate. sodium hydroxide, sodium bicarbonate, calcium hydroxide, etc., sufficient to give the mixture'a pH of from 5.5 to 8. An excess of alkali over-that sufficient to combine with the free acids present is usually avoided, since lsuch excess of alkalitends to cause hydrolysis .of the valuable esters present. Neutralization is ordinarily carried out at temperageous to observe the distilling temperature durthe fraction distills will serve to differentiate it manner described above, it is possibleto collect fairly large fractions rich in acetol acetate and in f an acetoxy-oxo-butane, respectively, which two ing the collection of the fraction, since at a given 3 pressure the general temperature range in which tures below 80 C. and preferably below 40 C. since, as hereinbefore mentioned, some of the components of the acetic oil tend to resinify or otherwise react to form by-products at higher temperatures, particularly under the conditions prevailing during neutralization. It shouldbe mentioned, however, that in the case of fractions rich in phenolic compounds it may be desirable to neutralize with a sufllcient amount of an appropriate alkali,A such as an alkali metal hy- Other fractions rich in acetol, acetic acid, butyric acid, and furi of the phenols may Bunicient water may/be to dissolve thesaltsV formed, although anexcess is preferably avoided f seinen! the neutral;components of; the v acetic oil are water-solubleandfiare'more easily f separated from the aqueous portion ofgthcifneuf` f -tralized vmixizurejiithe proportiongofl water kept'as small as convenient.` .After vthe neutralizatlon is complete, the non-acidic components from the solution 'of the salts formed during the neutralization. -Water-solublevv compounds,v such I fas sodium chloride, may be--added to the neu-- tralized mixture' to facilitate the separation, .al-

tionof the mixture'. I When neutral components soluble in the salt-solution are presentgthe separation is preferably accomplishedgbyextraction. v with an organic water-immisciblejsolvent.e. g.'vvv i with benzene, ether, ethyl acetate, carbon tetrachloride. etc. Alternatively, v a lsubstantially dry alkaline material" such asv powdered sodium carbonate may be used to neutralize the acids pres- .ent and the neutral oils separated from the solid salts of thev acid vcomponents by decanting or filtering.

The saltsV remaining v'after separation of the non-acidic components from the neutralized mixture may be treated in'any desired manner for the recovery of the acidic 'aqueous solution be rst freed from volatile components by distilling withsteam' and then acidiiled with a mini j usually forma distinct layer and arejsepa'rated' f though this is notususuy desirable whcnathc acids are to be recoveredffromitheaqueous porv lto'1.045l and; point-the'distilling teilnimmt ureI wasefl C. The ,f 1 collection of thesecond fraction was terminated nrstiraction'wa's "at this point andthe fraction, which weighed ,98.4pounds.' was found tobe rich in acetol.' ADisthe speelde-gravity then increased to tillationfwas continued until haddecreased'to 11.041-` and a l 1.059, atwhich point the distilling. temperature -.82 .5 'C,f The collection-,of the third fraction was-terminated at this point and thefraction, which weighed 89.9- pounds, was found to tillation was continued until the specific gravity terminated-.at point *fthe fraction, :which weighed y00.7 poundmfwas vfound to be rich-in acetic a continueduntil the specinc'gravity'had then increased .to, l.0 52,' at'wh'lph scid jnictmttion :mf

had increased ,to 1.086 "and then decreasedfto 1.055, at which point Ythe distilling temperature was 88.5 1C. Collection vof the fourth i'raction ,Iwas terminated at thisy point'k and the lfraction,

rich in furi'uraI.v Distillation was continued until `tilling temperature was 97.5 C; Collection of the fifth fractionv was terminatedy at this' pointfand ,the

j whichweighed. 85.9 pounds, was found be the specific gravity had decreased 4to 1.027 and -thenincreased `to 1.049 at which point the dis-v vfraction, which vwcihcda1-2 pounds was' .found to be richin' butyric acid. Distillation was continued untilthe speci'c gravity had increased point', thedistilling temperature iwas 108 C. The

components. Thus, of the salts may,for"example,'=

eral acid to. liberate the free acids. The free acids mayfthen be separated from the aqueous portion ofthe mixture, or the acidiiled mixturev 'may be extracted vwith a solvent, such as ethyl acetate, carbon tetrachloride or benzene.4 Alter-- natively, the acidiiled mixture may be'dlstilled with steam to remove the acidic components'and the latter lthen 'separated or .extractedfrom the distillate. The separated acids, or` the/ extract thereof, may then be fractionally ldistilled',toglie? sired, fbe further purified, e. g., by'refractionating,

usually under reduced pressure. VIn the case of r fractions neutralized after fractional distillation, l refractionation is preferably precededby ja rapid distillation under reduced pressure without reux to free the material from the last traces ofv salts. since prolonged heating oi' some of the ylessl heat-s'tableproducts in contact with such'salts cover the individual acids' inc high state of purity'.v The neutral fractions resultlng'from thegneu-f tralization and fractionaldistillation-may, itdemay cause considerable Idecomposition or resini'- u iication. l Certain advantages of the invention willbe vseen from the following examples, which are il-A lustrative and are not'to be construed as limiting the invention:

' Example 1 1 y 1360 pounds of yunneutralized"acetic oil-v were distilled at a pressure of 50 millimeters of mercuryl through an eiiicient fractionating column while v v maintaining a reiluxratio of. about 8 vto V1. The

specific gravity at 25v C. ofthe material distilllngl andthe ltemperature of the vvapor in the still head werenoted periodically. AThe specific' gravity vof collection' of the sixthy fraction Awas terminated fraction, which weighed at this fpo'int and the '122.6 pounds,

creased 4to 1.058, at whlc temperature was r118" C.'

during the ,collection eighth fraction was-terminated at this point and the fraction, which weighed 134.9'pounds was found to be rich in guaiacol. Distillation was continued until thel 4specific gravity had decreased tcbelow 1.062 and then increased to 1.078 at which point-the distillin'g temperaturewas 113..5 C.' The continued.l The speciilc gravity of the material collection -of the; ninth fraction due to the separationj4 of crystals of methyl cyclopentenolone L :uirtion was foundtolberich in creosol. v

was found to be rich in acetol'acef tate., Distilla'tlon was continued until theespe- 'ciiic'gravity had decreasedto 1.031 and then inv point the -fdistilling The collection of 'the seventh fraction was terminated at this point and the fraction, which weighed 1108.4 pounds was `'found tobe richjlnjan acetoxy-oxo-butane. 'ZDistillationwas continued until the specific gravity v n .had increased to 1.094 and then decreasdj-to'f-- 451.065 at' which point the -was lll C., thepressure of .the'fractio'n having b'eenlowered from 50 milllf "meters toabout 22 millimeters to avoid possible decomposition in the still.

distilling temperature l The collectionof-the i, v

collection of the ninth fraction was tervminatetl at this point and thedistillationdisdistilling vwas not taken continuously dl'lringthe *rromthchiatcrici distillihii` during. collection of a part of the fraction. The ninth fraction,` which weighed 84 poundswas iiltered and .the liquid "1 "to collected-in ,the manner described for the col -lction'cf thcnfth fraction in Example Lwcrc mixedjwith 15.3 pounds'of water'and neutralized with 5.5 pounds of sodium vcarbonate.- A j layer ofoily material was separated from the neutralized mixtureandthe aqueous salt layerwas distilled to remove traces of volatile non'- portion or' residue remained inthe the distillation',

1565 vpounds-,foi a fraction rich tate, collected in the manner described' for the .collection of the sixthA fraction in Example '1, were mixed'with'l poundsoi water and neu-1y .tralized to apH of 7' with 87 pounds of sodium -aeidic substances. The salt solution was thenacidiiled'with 5.3 pounds of 100 per cent sulturic. acid and the acidiiled solution was"- distilledk with steam to recover volatile acids.` 66 pounds then discarded. ,The ethyl acetate vfrom the extraction operation was iractionaily distilled and there was'thus recovered, in addition tothe I' ethyl acetate and aU small i'orefraction of acetic acid, 5.11 pounds of pure butyric-acid. e, .33 pound -1- Example carbonate while maintaining the temperature bestillat theend ol Y. theequivalent o! vemployed. v We therefore particularly point outand disvin acetol ace- .i f

fourthl fritctiinnfv which consisted'of l2,000 ce.Y ofa-liquid rich in an acetoxy-oxobutane. was tere I minated and the distillation discontinued. The

fractions rich in furfural and acetol acetate were reiractionated without further treatment to recoversubstantially pure vfurtural and acetoi'acetate, respectively. v

g s otnermodes f applying the principle or the invention may be employed instead ot those exg as regards the plained, change. being made method herein disclosed, provided the step or steps stated by any vof the following 'claims or such stated step or steps be tinctly claim as our invention:

v i.. In amethod i'or separating a componente! "fa-mixture selected from the consisting oi' lacetic oil and aceticoil which has been freed 20.

of acidic ingredients by neutralizationthe steps whichconsist `in fractionally distilling the mixlow 8 0'` C. Upon allowing the mixture to stand, an

aqueous and van oil layer formed and these were separated. The aqueous layer was steam distilled' to remove traces of: volatile non-acidic compounds and acidiiledand then treated for the recovery of. butyric acid in the same manner as the aqueous solution oi Example 2. The oily layer after separation from the aqueous layer weighed 1384 pounds. l It was distilled withoutfractionation at a pressure of millimeters of mercury and the distillate, which weighed 1266 pounds,

was then distilled at, a pressurev of 50millimeters ot mercury through an emcient fractionating column while mainta g a reflux ratio of about s to 1, and the fraction boiling at '100 C. col-v` lecte'd. 'The collected fraction weighed 462 pounds and was about 95 per cent pure acetol acetate.

'f Ewample 4 36.00000. ofacetic ou were' mixed with 36,000 ce.'

ture and beginning collection of a fraction of, distillate when the speciilc gravity of the material -distilling is receding from a region in which its direction of change was reversed and is approaching a region wherein itsaverage rate of change y with respect to the amount of material distilled is relatively small, continuing collection o1' the fraction-until the speciiicgravitypasses through the last-mentioned region and terminating collection of the fraction when the speciilc gravity 'is receding from said region.`

of a fraction of distillate when the specific gravity,

of the material distilling is recedingfrom a region of water land neutralized to a pHof '1 with 2,880 z grams of lsoglium carbonate lwhile maintaining the temperature of the'mixture below 40 C. An oily layer of 26,500 cc. was separated from'the mixture and distilled under reduced pressureI 'without .fractionation to free it from traces of v salts. The distillatewas then redistilled at a in which its direction of vchange was reversed'and I is approaching a region wherein its average rate of change with respect to the amount oi material distilled is relatively small, continuing collection of the fraction until the specic gravity passes through the last-mentioned 'region and terminating collection of the fraction when the speciilc 'pressure of 50 millimeters of mercury through.

an eiilcient fractionating lcolumn while maintaining a reux ratio of about 10 tol.v The speclc vgravity at 25 c. of the material distilling and,

specic gravity of the material distilling had in creased to 1 .112 and then decreased to Y1.082 and point, collection of the second. fraction, which consisted of 2,500 cc. of a liquid rich in furfural.

was terminated.. Distillation was continued un til the speciic gravity after decreasing to 1.069 hadchanged relatively little during the collection Aoiseveral thousand cubic centimeters of distillate temperature was 103 C. At this point the col- `Vlection ofthe third fraction,j which consisted o i' '3,700 cc.' of a .liquidrich in acetol acetate was A vilrst or foreeiractionof f i the Adistilling temperature was 84 C.' At this a l. and had then decreased to 1.050, and the distilling terminated'. Distillation was continued until the' speciilc gravity had decreased to 1.035 and then increased to 1.065, and the distilling temperature was 114 C. At this point, the collection of the gravity is receding from said region.

FLOYD L. BEMAN,

f mh nENcEs crran 1 The following references are of record in the ille ot this patent: g f, 'UNrrEDsTA'rEsPA'rENTs- Number'v Name i Date 2,251,771 Wynn et al.. Allg. 5, 1941 1,580,144 Legg et al.. Apr. 13, 1926 1,868,102 Henderson et al. July 19, 1932 1,928,746 Wilson a Oct. 3, 1933 2,290,157l lBright July 21,1942

2,223,299 f Chesley' Nov. 26, 1940 f rortalciNrarnn'rs' Number Country 7 Date 376,009 British July 7, 1932 OTHER REFERENCES Industrial and Engineering Chem., v ol. 9, pp.

462-464 (May 1917). Copy in Scientiflc-L1-v brary.)

Shriner an (1940), published by John Wiley 8: Sons, Inc. (Copy in Libra.y of Congress, pp. lOl-#105,.)

v 1.. Ina method for separating'a component of acetic oil the steps which consist in fractionally y distilling the acetic oil and beginning collection d Fuson, Y'I'he Systematic Idenl tication of .Organic Compounds, second edition 

